Download Groups of the Periodic Table

Periodic Table:
Atoms, Classification
& Representation
4 - CH 1
Review: The Atom
• What is an atom?
• Definition: An atom is the smallest particle of matter. It cannot be
divided chemically
• What are the parts of an atom?
• In the nucleus: Protons and Neutrons
• Outside of the nucleus: Electron
• Protons have a positive charge, neutrons have no charge, and
electrons have a negative charge
How Small is an Atom?
The Rutherford-Bohr Atomic Model
• Named after two scientists: Ernest Rutherford and Niels
Bohr
• Rutherford: Discovered that most of the atom is empty
space and contains a very small but dense nucleus
• Bohr: Electrons surround the nucleus in orbits (pathways)
but can move from one orbit to another
• Definition: A representation of the atom as a very small
nucleus made up of positively charged protons,
surrounded by negatively charged electrons moving in
defined orbits
Representing Atoms (Rutherford-Bohr)
• To keep things simple, protons and neutrons are
represented as a “ball” in the center (the nucleus)
• Electrons are arranged on orbits (also called shells or
valences) around the nucleus
• Each orbits has a MAXIMUM number of electrons it can
support
• The number of protons and electrons are EQUAL and we
know this number as the ATOMIC NUMBER
How Many Electrons?
• For the first 20 elements:
• 1st orbit = 2 electrons
• 2nd orbit = 8 electrons
• 3rd orbit = 18 electrons BUT after 8 electrons the 4th begins to fill too…
• Examples:
• Helium: Atomic Number = 2
• Aluminum: Atomic Number = 13
• Calcium: Atomic Number = 20
Example of an Exam Question
• Which of the following best represents the aluminum (Al)
atom according to the Rutherford-Bohr model?
Representing Atoms (Lewis Notation)
• A simplified representation of the atom
• Only valence electrons are shown
• Valance Electrons: the electrons located FURTHEST from
the nucleus
The Periodic Classification of the
Elements  The Periodic Table
• Periodic Classification: A way to group the elements
according to certain properties
• Periodic Table of Elements: a visual presentation of the
elements in groups according to their physical and
chemical properties
Review: Physical vs Chemical Properties
• Physical Property: A property that can be observed or
measured without changing the make-up of the matter of
the object (ex: colour, odor, texture, density, melting point,
boiling point)
• Chemical Property: Cannot be determined by simply
viewing or touching the object; only becomes evident
during a chemical reaction (ex: reactivity with other
chemicals, flammability, heat of combustion)
Periodic Table Organization Activity
• Each team will be given a collection of shapes
• Each shape (piece) has two numbers on it
• You task is to decide how to best organize ALL of the
pieces into one table where each row (goes across) and
each column (goes up and down) share similar
characteristics (you cannot simply put them in a single line)
• When your team is done, you will have a work sheet to
complete based on the activity.
How the Periodic Table is
Divided/Organized
• Each element has its own box/square
• For each element:
• Symbol of the Element: This is universal (same for all languages)
• Atomic Number: always located at the top
• Atomic Mass: always located at the bottom
• Name of the Element: Written in the language of the document
First Major Division: Metals, Non-Metals
& Metalloids
• All the elements can be placed into these three
categories
• The “staircase” helps locate and identify the categories
Metals
• Location: To the LEFT of the staircase
• Properties:
• Conduct heat and electricity well
• Ductile (can stretch)
• Malleable (can bend)
• Usually shiny
• Solid at room temperature EXCEPT for Mercury (liquid)
Non-Metals
• Location: To the RIGHT of the staircase EXCEPT for
Hydrogen
• Properties:
• Poor conductors of heat and electricity
• Many are gases at room temperature
Metalloids
• Location: Found along the “staircase”
• Properties:
• Only 7 in total (Boron, Silicon, Germanium, Arsenic, Antimony,
Tellerium, Astatine)
• Have some properties of metals AND some of non-metals
• Some are very good conductors, others are very poor – used as
semiconductors in circuits and lasers
Groups of the Periodic Table
• All the elements found in one COLUMN (going up and
down) belong to a GROUP
• All elements in a group have:
• Similar chemical properties
• The same number of valence electrons
• Groups are labeled using Roman numerals (1 = I, 2 = II) and
either A or B
• “A” = main elements (biggest columns)
• “B” = transition elements (short columns)
• Roman numeral = number of valence electrons
Alkali Metals
• Location: The first column on the left of the periodic table
(except Hydrogen)
• Properties:
• Soft
• HIGHLY reactive metals
Alkaline Earth Metals
• Location: The second column on the periodic table
• Properties:
• Highly malleable (soft)
• Reactive
• Burn easily in the presence of heat
Halogens
• Location: The second-last column on the
periodic table
• Properties:
• Non-metals
• React easily to form compound
• Commonly form salts
Noble Gases (Inert Gases)
• Location: The final column of the periodic
table (on the right)
• Properties:
• Very stable, do not react well
• Commonly found in nature
The Periods of the Periodic Table
• Elements found in each row (going across) have the same
number of shells around the nucleus
• The period number corresponds to the number of electron
shells